Osteoid osteoma of the patella simulating knee arthritis: Case report

Osteoid Osteoma (OO) is an uncommon benign tumour and causes severe pain, being worse at night, and it responds dramatically to nonsteroidal antiinflammatory medications. An osteoid osteoma of the patella is very rare and if it arises, close to chondral surface differential diagnosis may be challenging. Patients with OO of the patella often present with knee pain that is also a typical symptom of trauma or of other diseases such as arthritis, which are much more common than OO. We present the case of a 19-year-old woman, basket-ballplayer, with a three year history of intense Anterior Knee Pain (AKP) that was first attributed to arthritis. A CT scan was performed that revealed the localization of an osteoid osteoma of the patella. The patient was successfully treated with open surgical technique, and the diagnosis was confirmed after histopathologic analysis. After one year of treatment, there was no relapse of the pain and no residual recurrent tumour. This unusual locati on was at the origin of unexplained pain and delayed diagnosis made so later. Although a rare entity, OO of the patella with its atypical clinical features could be included in the differential diagnosis of persistent anterior knee pain in the young adult. High clinical suspicion is necessary to avoid delay in diagnosis and irrelevant procedures for the patient. Key words: Osteoid osteoma, Knee pain, Intra-articular, Patella, Tumour resectio